摘要:

The fabrication of scanning tunneling microscopy (STM) tips by dc downward electrochemical polishing and ion milling has been investigated. The influence of parameters, such as voltage, immersion depth, cutoff time, and solution concentration, on the shape and sharpness of electropolished W tips are presented. Both electropolished and ion milled tips, which were characterized by transmission electron microscopy (TEM), were tested on Au films deposited on 〈100〉 oriented Si. The effects of tip radius on STM images are discussed thoroughly, and the results are also compared to atomic force microscopy (AFM) and TEM images.

ISSN:0734-211X    

DOI:10.1116/1.589029

出版商:American Vacuum Society    

年代:1996

数据来源: AIP

摘要:

This article describes the configuration and application of an image processing software developed for extracting periodic atomic features from scanning tunneling microscopy (STM) images. This was done with a view to calibrating the lateral and/or vertical scale of images acquired by a STM with two tunneling units, where a crystal can be used as the scale reference with one of the tunneling units. The image processing software was applied to consecutively acquired images of graphite with a size of 150×5 nm. The number of lattices automatically counted in a line scan of 150 nm, scanned in 400 ms, showed a matching of 99.95% from one image to the other. On the other hand, the matching in the feed direction, where image width was only 5 nm, but took 240 s, was 95%. As an example of application of the developed software, nonlinear movement of piezoscanners were readily monitored in the 100 nm order.

ISSN:0734-211X    

DOI:10.1116/1.589038

出版商:American Vacuum Society    

年代:1996

数据来源: AIP

摘要:

Gold oxide films were prepared by reactive sputtering of pure gold in an oxygen plasma. These films were characterized by chemical and physical means to better understand the behavior of this metastable compound. Gold oxide, Au2O3, decomposes into the elements at 350 °C. It does not react with dry carbon dioxide but does form a metastable bicarbonate in the presence of moisture and CO2, releasing oxygen and eventually reverting to elemental gold. Gold oxide was generated by reactive sputtering along with silica in an oxygen plasma from Au–Si solidified alloys. Gold oxide decomposed upon pyrolysis to produce composites showing different characteristics depending on the gold content. Composites containing about 95 wt % gold produced reflective, conductive, and adherent films. Composites derived from an alloy containing 5 at. % gold produced a nanostructured material with gold clusters of about 5 nm in diameter dispersed in a silica matrix. This nanocomposite showed high resistivity, and capacitance with a dielectric constant of 400.

ISSN:0734-211X    

DOI:10.1116/1.589020

出版商:American Vacuum Society    

年代:1996

数据来源: AIP

摘要:

This article reports on the use of atomic force microscopy coupled with a simple wet chemical sample preparation to characterize processes involved in the realization of 0.4 μm metal on silicon contacts. Photolithography and contact etching processes both lead to high aspect ratio topography (≳4). The samples are imaged after a preparation which removes the high aspect ratio and leads to a better image. The main parameters of this new procedure are highlighted in this report, namely contact area for lithography and etching processes and silicon consumption for the etching process. The contact silicidation process is also monitored, and the electrical results are correlated with the silicide thickness formed in the contact.

ISSN:0734-211X    

DOI:10.1116/1.588452

出版商:American Vacuum Society    

年代:1996

数据来源: AIP

摘要:

The effect of thermal annealing on the surface morphology of thin gold films is studied using a scanning tunneling microscope (STM) and computer simulations. The gold films were thermally evaporated onto glass substrates, and were then measured with the STM at room temperature before and after annealing. The annealing treatments were done at temperatures between 200 and 500 °C and for periods ranging from 1 to 200 h. We present data showing the evolution of the average surface‐grain size and root‐mean‐square roughness amplitude of the gold films as a function of annealing temperature and duration. Our data suggest that surface diffusion is the main process active at low annealing temperatures of 300 °C and below. At higher annealing temperatures grain coarsening, which can be explained by recovery and recrystallization (secondary grain growth), is the dominant process contributing to large scale morphology changes. Computer simulations based on these processes account well for the experimental results, with activation energies of about 1.0 and 1.4 eV, for surface self‐diffusion of gold and grain coarsening, respectively.

ISSN:0734-211X    

DOI:10.1116/1.588467

出版商:American Vacuum Society    

年代:1996

数据来源: AIP

摘要:

A monodomain monolayer of adsorbed liquid crystal molecules was observed by scanning tunneling microscopy (STM). Voltage pulses applied to the STM tip while scanning caused formation of rotated domains in the two‐dimensional crystalline monolayer. The new domains annealed out over several minutes, reforming the initial monodomain. This shows that the STM tip can influence the structure of adsorbed monolayers and suggests that the voltage pulses often used to achieve images of organic adsorbates may influence monolayer formation and not simply reshape the STM tip.

ISSN:0734-211X    

DOI:10.1116/1.588480

出版商:American Vacuum Society    

年代:1996

数据来源: AIP

摘要:

The soft x‐ray reflectivity of multilayer films is affected by the surface roughness on the transverse nanometer scale. Scanning tunneling microscopy (STM) is an ideal instrument for providing high‐lateral‐resolution roughness measurements for soft x‐ray multilayer films that cannot be obtained with other types of instruments on the transverse nanometer scale. The surface roughnesses of Mo/Si, Mo/C, and W/Si soft x‐ray multilayer films prepared by an ion‐beam‐sputtering technique were measured with a STM on the vertical and transverse attributes. The film roughnesses and average spatial wavelengths added to the substrates depend on the multilayer film fabrication conditions, i.e., material combinations, number of layers, and individual layer thickness. These were estimated to lead to a loss of specular reflectivity and variations of the soft x‐ray scattering angle distribution. This method points the way to further studies of soft x‐ray multilayer film functional properties and can be used as basic guidance for selecting the best coating conditions in the fabrications of soft x‐ray multilayer films.

ISSN:0734-211X    

DOI:10.1116/1.588488

出版商:American Vacuum Society    

年代:1996

数据来源: AIP

摘要:

Scanning tunneling microscopes allow the formation of structures, by the application of voltage pulses between tip and sample whose dimensions are in the range of some nanometers. Systematic investigations have been carried out on the Si(111)‐7×7 using W and Au tips in order to better understand the physics of the underlying deposition process. Therefore the voltage pulse, current, andz‐piezo voltage were measured as a function of time. Above a threshold voltage, which depends on the pulse duration and the tunneling current, too, hills were created in the range between 5 and 25 nm. The surface structure was preserved up to the hills. Further, there is a linear dependence of the diameter on the pulse amplitude and pulse duration. A fit of the data gives a slope of (0.1±0.02) nm/s for tungsten tips and (0.45±0.14 nm/s) for gold tips, respectively. In addition, there is also a logarithmically dependence of the diameter upon the tunneling current for both tip materials. The results obtained are discussed with reference to the formation mechanisms published to date. None provide a satisfying explanation of our results.

ISSN:0734-211X    

DOI:10.1116/1.588501

出版商:American Vacuum Society    

年代:1996

数据来源: AIP

摘要:

Electron radiation induced hydrocarbon contamination can be either a problem or a useful tool in electron beam analyses and lithographies. We have used atomic force microscopy to study electron beam written contamination structures. Contamination is shown not only to arise from the primary electron beam but also from the energy scattered outside of the direct impingement area. The size of the contamination structures correlates well with that expected from electron scattering theory. By varying the geometry of the written structures, the rate at which the electron dose is deposited, and the nearby hydrocarbon surface density, we show that surface diffusion of hydrocarbon molecules plays a primary role in the formation of the contamination structures.

ISSN:0734-211X    

DOI:10.1116/1.588429

出版商:American Vacuum Society    

年代:1996

数据来源: AIP

摘要:

A multiple‐layer blank structure with two shifter layers coated on a quartz substrate is proposed for the fabrication of phase‐shifting masks. The thickness of these shifter layers is such that they induce a 180° phase shift of light compared to air. On top of these shifter layers, an opaque layer is coated. The top shifter layer is patterned during the fabrication of the phase‐shifting mask. The bottom shifter layer is patterned only to repair missing shifter defects. But the main purpose of this bottom layer is to act as an etch layer or give an end point during the repair of the phase defects or during the fabrication of the mask. Using yttrium fluoride etch stop/end point layer (bottom shifter layer), we have demonstrated the feasibility of multiple‐layer blanks. This layer acts as an etch stop during the patterning of the main shifter layer and has a good refractive index match to that of quartz. The phase‐shifting masks made using this multiple‐layer blank structure have shown lithographic performances comparable to those of standard phase‐shifting masks.

ISSN:0734-211X    

DOI:10.1116/1.588435

出版商:American Vacuum Society    

年代:1996

数据来源: AIP